In various applications, corrosive or reactive fluids are allowed to invade the interior of a dynamoelectric machine. Such corrosive or reactive fluids may be used for lubrication, cooling and/or driving a turbine for purposes of turning an alternator to supply electrical power. One problem encountered in such applications is related to the necessity of isolating the stator assembly from the corrosive or reactive fluid.
In one particular application, a dynamoelectric machine has been proposed to serve as a power supply for the Space Station. It is contemplated that, in such an application, a corrosive or reactive fluid such as toluene is heated indirectly by means of solar energy and passes through nozzles in gaseous form to cause a turbine to spin thus turning the alternator to supply electrical power in what must necessarily be a closed cycle system. In such a closed cycle system, it is important to avoid loss of system working fluid and to avoid contamination of the immediate surroundings.
Because of such requirements, the working fluid portion of the dynamoelectric machine must remain sealed. Also, due to the particular requirements of the Space Station, the dynamoelectric machine should be capable of maintenance-free operation for extended periods of time, e.g., on the order of 10 to 30 years. However, when toluene is utilized as the working fluid, insulating materials can be softened and seriously degraded by the toluene. Likewise, toluene can be contaminated by outgassing from the insulating materials.
Because of the corrosive or reactive nature of toluene, a shielding member is advantageously disposed between the rotor and the stator. Such a shielding member, which may suitably define a rotor cavity separated from the stator, must be non-magnetic, non-conductive, non-porous and non-outgassing. In addition, the shielding member must be capable of handling corrosive or reactive fluids at operating temperatures on the order of 250-400.degree. F.
In the past, dynamoelectric machines containing shielding members have typically isolated the working fluid from the windings particularly where the working fluid was oil or liquid metal. However, shielding members in such machines would not work with corrosive or reactive fluids such as toluene, Freon, ammonia, and other organic fluids that are normally considered to be solvents since the resinous insulating materials conventionally employed in such shielding members would degrade in such working fluids and the shielding member would not prevent outgassing with the working fluid. Accordingly, it has remained to provide a shielding member in a dynamoelectric machine that is capable of utilization with corrosive or reactive fluids.
Among the early attempts to provide a shielding layer is that disclosed in Washizu et al U.S. Pat. No. 4,227,108 which is formed by an aggregate-containing glass compound on an inner surface of the center bore of an annular laminated stator core. Also, Dochterman U.S. Pat. No. 3,867,658 discloses barrier means in the form of a sleeve made from ceramic material and Janotik U.S. Pat. No. 4,153,868 discloses the utilization of a non-conductive ceramic material to cover the surface area defining a stator opening. Moreover, Hobart U.S. Pat. No. 1,543,502 discloses a three-piece partition formed of end flanges with the center portion comprising a non-magnetic material and Madsen U.S. Pat. No. 3,366,813 discloses a glass fiber reinforced hollow cylinder in which metal end pieces may be used.
The present invention is directed to overcoming the above-stated problems, advancing the state-of-the-art, and accomplishing the stated objects.